1. Field of the Invention
The present invention relates to a method and an apparatus for measuring an operating position in a remote inspection, and in particular relates to a method and an apparatus for measuring an operating position to grasp data, such as a position and a length, of a reference point for an object to be inspected or repaired in a place, such as a nuclear reactor, that is difficult for workers to approach.
2. Background Art
Generally, in order to grasp an inspecting position or operating position in a structure or plant, a method in which workers approach a place to be inspected and measure an object using a scale is employed. However, in the case of inspecting and repairing the interior of a pressure vessel of a nuclear reactor or the like, since the workers can not directly approach an object to be inspected, the measurement of its position must be done indirectly by applying some measuring technology.
Conventionally, in the case of measuring a position and a size of a crack in an inner surface of, for example, a shroud for a nuclear reactor, a method has been employed, in which a camera and a lighting are placed in water, a reference structure used as a scale is utilized separately, and an object to be measured is photographed by the camera together with the scale, whereby a position and a size of the crack can be read by comparing the object with the scale from the image.
In recent years, a new standard for maintenance has been provided with respect to the nuclear reactor, resulting in increase of the need for more accurate inspection in the reactor. In this respect, with the conventional measurement using a camera, it was difficult for an inspector to accurately know the really inspecting point from an image displayed on a screen. This is significantly problematic.
To address this problem and enhance accuracy and efficiency of the measurement, there is a method for measuring a position, a shape and dimensions of an object to be inspected by providing a plurality of driving shafts as an robot arm and calculating the position of each driving shaft (Patent Document 1). Also, an approach in which the same target is observed in the three dimensions using a plurality of cameras in order to measure relative distances has been proposed (Non-Patent Document 1).
One example of the prior art for measuring a position and dimensions according to the Patent Document 2 will be described with reference to FIG. 19.
FIG. 19 illustrates a measuring apparatus for use in a method of measuring a position and dimensions by using a three-dimensional or stereoscopic observation. In this measuring apparatus, two light sources 2 for illuminating an object to be measured and two underwater cameras 3 are attached to a distal end of an articulated robot arm 1.
In the measuring apparatus constructed as described above, the positions of the underwater cameras 3 at the distal end are calculated from the displacement amounts of the respective shafts of the arm 1 from a reference structure in a nuclear reactor, and the three-dimensional size is grasped by a stereoscopic observation using the two underwater cameras.